Introduce arch-specific checker tests.

- The '.cfg' output is now created on target.
- Arch-specific checker tests can be created by inserting a
  suffix. For example:
      /// CHECK-START-ARM64: int Main.foo(int) register (after)
      /// CHECK-DAG:   <<Arg:i\d+>>     ParameterValue

Change-Id: I55cdb37f8e806c7ffdde6b676c8f44ac30b59051
15 files changed